Less than 50 monks met with 200 police, who were armed with rifles, shields and electric batons, witnesses said.

The monks were carrying a petition demanding the release of jailed Khmer Kampuchea Krom monks in Vietnam, including defrocked monk Tim Sakhorn.

Tim Sakhorn has been in jail since his disappearance from a Takeo province pagoda in July.

The Khmer Kampuchea Krom Human Rights Organization and the rights group Adhoc said in a statement police stopped the monks from entering the Vietnamese Embassy.

Chan Saveth, a rights worker for Adhoc, called the clashes "very brutal."

Police chased monks and beat them, he said, while monks hurled water bottles at the police.

The groups said six monks were seriously hurt and 10 received minor injuries.

Buddhist monk Thach Mony called the clash an act of godlessness.

"The use of violence on the monks, I think it is wrong, it does not look good, and it is illegal," he said. "They are monks, and they should not do that.

[The monks] have nothing, they do not have weapons, yes, and [the police] used violence on them, using batons to assault them." The monks were not demonstrating, he said, but trying to deliver the petition.